The Minolta 50mm f/1.7 is a fine lens for what you want to do. Itcosts &lt;$100, andhas the largest available aperture except the 50mm f/1.4 which costs $350, or the 35mm f/1.4 which costs $1,200. There are other fast lenses for a Sony dSLR, but none are as fast and as reasonably priced.

I also have to ask - what is your subject? Lenses cannot create light - and even 1.4 lenses won't provide high enough shutter speeds if the lighting is really poor. So what types of night time photographs are you wanting to take?

A couple of points on the subject. First, the price in the UK is always higher than in the US.

IMO, a 50mm lens with a cropping factor of 1.5x is really 75mm, which is very very tight for indoor photography (unless you are shooting single subjects). So, although the 50mm 1.7 is a fast lens, for me its FL is very limiting. I'd prefer a slower (but wider) lens and either increase the ISO or use flash in low light situations. But, that's me.